Various high-frequency heating apparatuses in which a steam generator is provided and which execute a heating process, supplying steam to a cooking chamber which is a high-frequency heating chamber. Of such high-frequency heating apparatuses provided with a steam generating function, there are some provided with a water tank for supplying water to a steam generator for suitably supplying steam required for a heating process to a high-frequency heating chamber. In that case, a water residual quantity sensor is provided to the water tank to detect that the water tank contains water and a transparent window is provided to the water tank to enable a user to check whether the water tank contains water or not.
However, it can be checked by the residual quantity sensor and the transparent window whether the water tank contains water or not, however, it cannot be verified when the water was supplied to the water tank and a sanitary problem may be caused. It can be checked whether the water tank contains water or not, however, there is a problem that it cannot be judged whether the quantity of the water is enough for next cooking or not. The water residual quantity sensor provided to the water tank requires adjustment and maintenance, the number of parts is also increased and the cost is increased.
To solve such problems, simply, water in a water tank is replaced every heating process and after the water tank is filled with new water, a heating process has only to be executed. However, there is a problem that in continuous heating, it is very troublesome and inefficient to detach a water tank and replace water in the water tank every heating process. There is a problem that the constant control of the quantity of water in a water tank requires that a power source of an electronic oven is normally kept turned on and there is a problem that the constant control prevents power saving.